Membrane proteins and peptides are extremely important to understanding human health and treating disease. Membrane proteins make up 30% of all proteins in the body,7 are involved in regulating signal transduction and molecular transport into and between cells, and are the target of most drugs available today.8 To function properly, membrane proteins must be embedded in a lipid bilayer. Well-controlled studies of individual membrane proteins or peptides require creating an artificial lipid membrane to hold the protein or peptide, but existing methods for producing artificial membranes, such as the black lipid membrane and membranes with solid support, cannot be adapted to high-throughput techniques because the membranes are quite delicate as in the case of black lipid membranes or have limited access to one of the two sides of the bilayer for membranes riding on a solid support. High-throughput methods, which allow examination of a large number of compounds or a large number of interactions simultaneously, are increasingly being used to study molecular interactions affecting human health and to identify and test drugs. The importance of high-throughput screening has been recognized in the NIH Roadmap for Medical Research. The Molecular Libraries and Imaging portion of the NIH Roadmap seeks to facilitate the development of new, small-molecule drugs within the public sector. High-throughput screening of these small molecules is an integral part of the proposed effort.
We have developed and disclose a method for studying lipid membranes and membrane proteins or peptides based on an inverted emulsion manipulated by a laser. With this method we can readily produce bilayer membranes with small volumes and small surface areas. This method is easily adapted to high-throughput screening of membrane protein function and drugs influencing membrane proteins or peptides. Because of the small size of the membrane, this technique avoids the membrane fragility issues typical of black lipid membrane techniques, and because the membrane is formed between two inverted emulsion droplets, we avoid the difficulties in accessing both sides of the membrane found with artificial membranes on solid supports. With the small volumes involved, we can minimize the quantities of reagent used in assays and can perform very large numbers of assays rapidly on a single substrate. The combined optical manipulation and readout make for a relatively simple yet quite flexible assay platform. Some of our results on introduction of lipid vesicles in the aqueous phase of the emulsion has also been demonstrated in a publication by the Bayley group.9 